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Osteocalcin increases muscle performance, but naturally declines as we age – but injections can reverse the age-related exercise capacity declinein mice.

Levels of the hormone osteocalcin naturally decline as we age
A hormone jab could get the elderly exercising like they were years younger, a new study found.
During exercise the bones produce a hormone called osteocalcin that increases muscle performance.
But levels of the hormone naturally decline as we age, beginning from the age of 30 in women and 50 in men.
A study by Columbia University Medical Centre identified the first bone-derived hormone known to affect exercise capacity.
It also showed osteocalcin injections can reverse the age-related exercise capacity decline in mice and the findings apply to humans.
Geneticist Professor Dr Gerard Karsenty said: “Our bones are making a hormone called osteocalcin that provides an explanation for why we can exercise.

“The hormone is powerful enough to reconstitute, in older animals, the muscle function of young animals.
“Muscles and bones are close to each other, but it had never been shown before that bone actually influences muscle in any way.”
The senior author noted during exercise in mice and humans, the levels of osteocalcin in the blood increase depending on how old the organism is.
He observed that in three-month-old adult mice, osteocalcin levels spiked approximately four times the amount that the levels in 12-month-old mice did when the rodents ran for 40 minutes on a treadmill.
The three-month-old mice could run for about 1,200 meters before becoming exhausted, while the 12-month-old mice could only run half of that distance.

“This may be one way to treat age-related decline in muscle function in humans”

To investigate whether osteocalcin levels were affecting exercise performance, Prof Karsenty tested mice genetically engineered so the hormone couldn’t signal properly in their muscles.
Without osteocalcin muscle signalling, the mice ran 20 to 30 per cent less time and distance than their healthy counterparts before reaching exhaustion.
Surprisingly, says Karsenty, when healthy mice that were 12 and 15 months old, and whose osteocalcin levels had naturally decreased with age, were injected with osteocalcin, their running performance matched that of the healthy three-month-old mice.
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The older mice were able to run about 1,200 meters before becoming exhausted.
Prof Karsenty said: “It was extremely surprising that a single injection of osteocalcin in a 12-month-old mouse could completely restore its muscle function to that of a three-month-old mouse.”
Normal “resting” levels of osteocalcin in the blood also declined with age in rhesus monkeys and humans, with the decline occurring about 15 to 20 years sooner in women than in men.
It has never been shown that bone actually influences muscle “in any way”

He added: “If you look backwards during evolution, men were much more active than women – for example, in hunting and fishing.
“That may be an explanation for why the decrease in circulating osteocalcin occurs later in men than in women.
The study also measured levels of glycogen, glucose, and acylcarnitines – an indicator of fatty-acid use – in mice with and without osteocalcin to determine the cellular mechanisms behind osteocalcin’s effects.
It found the hormone helps muscle fibres uptake and catabolize glucose and fatty acids as nutrients during exercise.
Prof Karsenty added: “It’s never been shown before that bone actually influences muscle in any way
“Osteocalcin is not the only hormone responsible for adaptation to exercise in mice and humans, but it is the only known bone-derived hormone that increases exercise capacity.
“This may be one way to treat age-related decline in muscle function in humans.”
The study was published in the journal Cell Metabolism.